PreSonus HP4

PreSonus HP4 4-Channel Studio Headphone Amplifier, Headphone level control for each channel, 4 stereo ¼” headphone outputs, 2 balanced ¼” line outputs, 2 balanced ¼” line inputs, Mono summing switch for each channel, Monitor level control, Monitor mute switch, Daisy-chain multiple units via monitor outputs, Compact 1/3U rack-mount chassis, Sealed, detented, metal rotary controls, External 16 VAC power supply, Dimensions: Height 1.75” (44.45 mm) x Depth 5.5" (139.7 mm) x Width 5.5” (139.7 mm), Weight: 5 lbs (2.27 kg).